1. Field of the Disclosure
The disclosure relates to a liquid crystal display device, and more particularly, to a two-way liquid crystal display device that displays images in both directions.
2. Discussion of the Related Art
Liquid crystal display (LCD) devices are most widely used for monitors of notebook computers, monitors of personal computers and televisions due to excellent moving images and high contrast ratio. LCD devices use the optical anisotropy and polarization properties of liquid crystal molecules of a liquid crystal layer to produce an image.
An LCD device includes two substrates spaced apart and facing each other and a liquid crystal layer interposed between the two substrates. The alignment direction of the liquid crystal molecules is controlled by varying the intensity of an electric field applied to the liquid crystal layer, and the transmittance of light through the liquid crystal layer is changed.
The LCD devices require an additional light source because the LCD devices are not self-luminescent. Therefore, a backlight unit is disposed at a rear side of a liquid crystal (LC) panel and emits light into the LC panel, whereby discernible images can be displayed.
Backlight units are classified into an edge type and a direct type according to the position of a light source with respect to the LC panel. In edge-type backlit units, one or a pair of lamps are disposed at one side surface or each of two side surfaces of a light guide plate. In direct-type backlight units, a plurality of lamps are disposed directly under an LC panel.
The edge-type backlight units are easily fabricated, are thin, have light weights, and have low power consumption as compared with the direct-type backlight units.
FIG. 1 is a cross-sectional view of illustrating a liquid crystal display (LCD) device including an edge-type backlight unit according to the related art.
In FIG. 1, the related art LCD device includes a liquid crystal panel 10, a backlight unit 20, a support main 30, a top cover 40 and a cover bottom 50.
The liquid crystal panel 10 displays images and includes first and second substrates 12 and 14 facing and attached to each other with a liquid crystal layer (not shown) interposed therebetween. Polarizers 19a and 19b are attached at front and rear surfaces of the liquid crystal panel 10 and control the polarization of light.
The backlight unit 20 is disposed at a rear side of the liquid crystal panel 10. The backlight unit 20 includes an LED assembly 29, a reflection sheet 25, a light guide plate 23 and a plurality of optical sheets 21. The LED assembly 29 is disposed at a side surface of the light guide plate 23. The LED assembly 29 includes a plurality of LEDs 29a emitting white light and an LED printed circuit board 29b, which will be referred to as a PCB and on which the LEDs 29a are mounted. The reflection sheet 25 is disposed over the cover bottom 50 and is white- or silver-colored. The light guide plate 23 is disposed over the reflection sheet 25. The plurality of optical sheets 21 are disposed over the light guide plate 23.
Light incident on the light guide plate 23 from the LEDs 29a is widely spread in the light guide plate 23 by being totally reflected several times, and is provided to the liquid crystal panel 10 as a plane light source.
Edges of the liquid crystal panel 10 and the backlight unit 20 are surrounded by the support main 30 having a rectangular frame shape. The top cover 40 covers edges of the front surface of the liquid crystal panel 10, and the cover bottom 50 covers a rear surface of the backlight unit 20. The top cover 40 and the cover bottom 50 are combined with the support main 30 to thereby constitute one-united body.
The edge-type backlight unit 20 has light weight and low power consumption and needs low driving voltages, and the edge-type backlight unit 20 is widely used for various electronic devices.
Meanwhile, two-way liquid crystal display devices, which display the same image or different images in both directions, have been actively developed.
The two-way liquid crystal display device, beneficially, includes the edge-type backlight unit 20 for its light weight and thin thickness.